<div id="app">
  <div :class="['box', {active: isActive}]">
    {{isActive?'大': '小'}}
    <button @click="isActive = !isActive">Toggle size</button>
  </div>
</div>
<script src="https://unpkg.com/vue@next"></script>
<script>
  Vue.createApp({
    data() { return { isActive: false } }
  }).mount('#app')
</script>
<style>

.box {
  width: 200px;
  height: 200px;
  margin: 30px;
  box-shadow: 0 0 4px 0px rgba(0, 0, 0, 0.2);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all .3s;
}
.box.active { transform: scale(1.2); }
</style>